x2-5x+1=0,试求x2+x-2

Question

x2是x的平方减5x加1对于0,求x的平方加x的负2次方.的值.
哪位高手帮帮忙???谢谢啊...*-*

Answer 1

化简x2-5x+1=0，将5x移右边，两边再同除x
得x+1/x=5
x2+x-2=x2+1/x2=(x+1/x)2-2=5*5-2=23

Answer 2

x^2-5x+1=0
X^2=5X-1
X^2+X^(-2)
=X^2+1/X^2
=5X-1+1/X^2
=[X^2(5X-1)+1]/X^2
=[(5X-1)^2+1]/X^2
=25X^2-10X+1+1
=[23X^2+X^2-5X+1+X^2-5X+1]/X^2
=(23X^2+0+0)/X^2
=23X^2/X^2
=23

Answer 3

好难算 算不出来 算了老半天

Answer 4

那难啊 ？？....偶都不会,你 上几年级俺给你个答案不 知道对不对
答案:2X-5